Novel BiOCl-C3N4 heterojunctions were synthesized through an in situ ionic-liquid-assisted solvent-thermal method, through which a highly dispersed heterointerface was formed with almost no loss of C3N4. The composites were characterized using X-ray diffraction, high-resolution transmission microscopy, scanning electron microscopy, nitrogen adsorption-desorption measurements, UV-visible light diffusion reflectance spectrometry, Fourier-transform infrared spectroscopy, and photoluminescence spectroscopy. The results indicated that BiOCl was dispersed on C3N4 to form heterojunction structures with high specific surface area and the ability to absorb visible light. The photocatalytic results for the degradation of methyl orange (MO) indicated that the most active heterojunction proportion is 1BiOCl:1C(3)N(4), which increased the visible light photocatalytic activity 3.3-fold relative to that of a sample of the mechanically mixed counterpart of this composition. The enhanced performance was induced by the high separation efficiency of photoinduced electrons from the LUMO of C3N4 injected into the CB of BiOCl. We also determined that the enrichment of holes in the HOMO of the C3N4 in the present BiOCl-C3N4 heterojunctions played a dominant role in the oxidation of MO. (C) 2013 Elsevier B.V. All rights reserved.